Instruction of individuals in athletic endeavors, such as golfing, bowling, and tennis strokes, for improved performance in those sports is accomplished by numerous methods. Verbal instruction to a student is common, and demonstration of a particular motion sequence by one skilled in the activity is also frequently used. More sophisticated methods and apparatus for teaching motion sequences in various activities are also known.
U.S. Pat. No. 4,015,344 to Michaels et al. discloses a method and apparatus for teaching physical skills using a video tape of an instructor performing in front of a mirror which shows the instructor's back and the reflected image of the instructor's front. The tape of the instructor is shown to a pupil who simultaneously views the tape and his own image in a mirror situated next to the protection screen.
Connelly, U.S. Pat. No. 4,337,049 describes a method for automated training of manual skills in which a student's performance parameters, i.e. position, velocity and acceleration of body parts and equipment, are monitored and compared with ideal values. The deviation between student and ideal values is determined and a training signal is provided when the deviation exceeds a pre-set limit.
Linn, U.S. Pat. No. 4,163,941, describes a method and apparatus for determining the velocity of the head of a golf club. This invention focuses on only one variable, velocity of the club, in a complicated motion sequence involving positioning of the club and body, rhythm of the swing, and coordination of various movements. As can be appreciated, the velocity of a golf club head is not always indicative of a successful swing. Therefore, it is desirable to provide instructive systems which are directed to multiple aspects of a motion sequence.
A system is disclosed in Haas, U.S. Pat. No. 4,137,566, for analyzing a student golfer's swing by sensing the position of light-emitting devices located at the joints of a student's body during the execution of a golf swing. This information is translated into a computer-generated representation of the student's swing for subsequent viewing by the student. While this system allows a student to see a representation of the entire motion sequence, it cannot accurately reflect many subtle movements of the motion because the representation is a stick figure.
Haas further discloses the concept of comparing a student's swing with either a prior swing of the student or with a model teaching motion by electrically generated side-by-side, overlay or other electrically generated display methods. A potential difficulty with such comparison, not addressed by Haas, is the synchronization of the two swings to allow for an accurate comparison.
McCollough, U.S. Pat. No. 3,408,750, describes a system for golf instruction which provides a master tape of an ideal golf form for viewing by a student and a camera to view a student's swing. A means for electrically overlaying the image of the student's swing with the model teaching motion is also provided. The superimposed images can be viewed by an instructor for comparison of the two motions to detect deviations from the teaching motion. McCollough further provides for recording of the electrically overlaid student and teaching motions for subsequent viewing by the student. McCollough does not recognize or address the problem of synchronizing the superimposed student and teaching motions.
The mechanical overlay of two identical images through a refractive medium to produce a stereoscopic effect is known. (See U.S. Pat. No. 4,422,720 to Sheiman.) However, no known references provide for the mechanical overlay of two distinct visual images for the purpose of motion teaching, as in the present invention.
In view of the foregoing, there is a need for a motion teaching system in which two different motion sequence images can be visually compared by optically overlaying in a mechanical fashion the images and which provides a means for synchronizing the two images.